The present invention relates to annular, tubular, cylindrical, ring-like, and belt-like films to be used as conveyor belts for conveying precision parts to a predetermined position with a high positional accuracy, or as sealing packages for packaging or containing products, and a method of manufacturing these films. The principal field of applications of the present invention is a functional part of an image forming apparatus.
The present invention particularly relates to a conveyor or image fixing film or belt for a toner carrier.
Conventional tubular film manufacturing methods are:
1) Extrusion hot-melt molding represented by blown-film extrusion; and
2) Casting in which a resin or a precursor of the resin is melted, a predetermined amount of the molten resin or precursor is coated on the inner and outer surfaces of a tubular mold, and the product is released after desolvation.
Also,
3) Japanese Patent Laid-Open Nos. 63-34120 and 63-34121 have proposed methods by which a sheet film is wound on a core and the inner surface of a hollow tubular body is lined with the sheet by fusing the two ends of the sheet, and
4) Japanese Patent Publication No. 55-35247 has disclosed a method of manufacturing a polytetrafluoroethylene tubular body.
In conventional hot-melt molding process 1), if a tubular film formed by blown-film extrusion is used as a film for a fixing device of an image forming apparatus, FIG. 24, the tubular film is undesirably crushed when taken up.
In casting process 2), to obtain a uniform-thickness film there are problems of the concentration control of a solution, adjustment of the drying atmosphere, and the solvent treatment cost in the drying step.
In method 3) of lining the inner surface of a hollow tubular body, a lining layer with a uniform thickness can be obtained. However, when the lining layer is released from the inner surface of the hollow tubular body in order to obtain a tubular film, the lining layer is difficult to release because the adhesion with the hollow tubular body inner surface is strong.